Over a decade ago, Iain Duncan Smith found his newly free time being consumed by the issue of social justice. He explored the problems, studied the solutions and argued relentlessly for the Conservative Party to recognise the need for action. He did so from the backbenches, which offered him greater freedom (he is so closely identified with the Work and Pensions brief now, it’s easy to forget that he never shadowed the role under Cameron – that post was filled by Hammond, Grayling and Mayfrom 2005-2010).

When the Coalition came, though, IDS entered the Cabinet and proceeded to put into action many of the ideas which he had come to believe would offer those left behind by the modern economy or trapped in poverty by the flaws of the welfare state. Thanks to his resignation, we now know more about the battles with the Treasury that he fought in order to retain the budget required to make those policies successful. It evidently wasn’t easy, but for almost six years he plugged away at it – and in so doing, he played a major part in the remarkable increase in employment seen in recent years.

He obviously doesn’t think that the job is complete, however. And if any of his critics had hoped that he would now either focus solely on the EU referendum, or slip into retirement, they will be bluntly corrected by his article in today’s Times. It sets out a series of concerns and a set of principles which are probably best read as a challenge to the next leader of the Conservative Party:

‘…it is essential to ask if the right is always as ready to recognise the benefits of building up the people at the bottom, too. I don’t mean a paternalistic, feed-and-forget compassion. I mean “respecting”. As Winston Churchill urged: do we seek to recognise the treasure within every human person, and hate when that treasure remains buried and undiscovered? Are we, for example, as worried about the marginal tax rates that trap people in unemployment as those that disincentivise higher rate taxpayers?…The prime minister and his ministers can be proud of what they have already done but as a government and party we cannot allow a balanced conservative message to slip and narrow.’

In the piece, he reiterates some of his long-standing policies, such as the need for a more detailed and nuanced measure of poverty – particularly by recognising that the affordability of housing and the absence of worklessness are useful to illuminate the shadows cast by the blunt accounting of total GDP.

In terms of fiscal priorities, he shares the assessment of the ConservativeHome Manifesto that in a time of austerity and continued borrowing, and tax cuts should be focused first on those at the bottom of the heap. In a warning shot to the Government, the article echose his resignation letter in arguing that Tories must “ensure that austerity measures share out the pain more fairly” (though there aren’t any proposals for which budgets should be the particular targets for these fairer cuts).

Most intriguingly, Duncan Smith opens a new front by calling for “the dismantling of crony capitalism”. He is of course right – I’ve argued the same on this site – but this is a relatively new refrain. In his development of a centre right case for social justice, he has always rejected the futile and harmful envy of the left. Punishing success does nothing to defeat poverty, after all. While his opponents caricature him as an advocate of the Victorian concept of the “undeserving poor”, he has always been careful to reject that idea, too. Instead, he is now focusing his ire on the very opposite – the undeserving rich.

There’s an economic and social rationale for this attack – industries which are bound up in subsidies, economies which are distorted by government picking winners and businesses which are mis-managed due to rewards for failure are bad for all of us. But there’s also a political logic – just as IDS has long argued that Conservatives can benefit from defying the stereotype that we don’t care about those at the bottom, now he proposes we destroy the unfair assumption that we will turn a blind eye to dodgy behaviour at the top.